(a) Field of the Invention
The present invention relates to a detection process performed in a detector, and more particularly, to a detection process performed in a detector that is suitable for use in a residential security and automation system with improved functions.
(b) Description of the Prior Art
Pyroelectric infrared sensors have been used in the residential security and automation systems for years, rendering the systems able to activate or deactivate the switches mounted therein upon detecting a slight motion of human body in the designated areas. The so-called slight motion of human body may refer to any change in the gesture of a human object, such as shaking or nodding head, wiping nose and waving hand. Pyroelectric infrared sensors are particularly useful in the residential automation systems, since the electronic appliances placed under the management of a sensor of this type will continue to operate (for example, a continuous turning-on of a light source) as long as the human object keeps in motion during his stay within the monitored area.
However, problems may arise due to the passive operation manner of pyroelectric infrared sensors. That is to say, as a human object moves into the area monitored by a pyroelectric sensor, the infrared radiation emitted from the human object is focused by a lens array onto the sensor face and, as a result, the pyroelectric material mounted on the sensor face detects an energy change and generates a signal to place the corresponding circuits in an electrically conductive state, thereby activating the corresponding appliances. The pyroelectric sensor will nevertheless cut off the circuits on the occasion that the human object stays motionless for a period of time.
In other words, a pyroelectric sensor outputs signals only when the human object keeps in motion. While the duration of an activated lighting can be prolonged by extending the electrical conduction period of the corresponding circuits, slight motions still have to be made once in a while to keep the circuits in an electrically conductive state. For example, when a person enters a room monitored by a sensor, the sensor outputs a signal to activate lighting upon detecting the infrared energy emitted by the person in motion. If the person is motionless afterwards, the circuits for the lighting will be cut off and the lighting will be deactivated due to the incapability of the sensor to detect the presence of a motionless object. As such, the person has to make slight motions occasionally as a means to enable the sensor to detect an energy change and generate activation signals, thereby maintaining the lighting. Moreover, any strategy that involves extension of the duration of an activated lighting is undesirable in the sense of energy saving, because the lighting will last for a long period of time even after the exit of the person from the monitored area.
The conventional ways to overcome the problems mentioned above are mainly to reduce the threshold value for the signals retrieved from the sensors. While the sensitivity of a given sensor may show an increase upon decreasing the threshold value, there comes along an increased number of false actions. The crux of the invention is directed to providing an improved detection process without increasing the occurrence of false actions.